diff --git a/swh/storage/tests/storage_data.py b/swh/storage/tests/storage_data.py
--- a/swh/storage/tests/storage_data.py
+++ b/swh/storage/tests/storage_data.py
@@ -199,7 +199,9 @@
         'fullname': b'Nicolas Dandrimont <nicolas@example.com> ',
     },
     'date': {
-        'timestamp': 1234567890,
+        'timestamp': {
+            'seconds': 1234567890,
+            'microseconds': 0},
         'offset': 120,
         'negative_utc': False,
     },
@@ -209,7 +211,9 @@
         'fullname': b'St\xc3fano Zacchiroli <stefano@example.com>'
     },
     'committer_date': {
-        'timestamp': 1123456789,
+        'timestamp': {
+            'seconds': 1123456789,
+            'microseconds': 0},
         'offset': 0,
         'negative_utc': True,
     },
@@ -253,7 +257,9 @@
         'fullname': b'tony <ar@dumont.fr>',
     },
     'committer_date': {
-        'timestamp': 1123456789,
+        'timestamp': {
+            'seconds': 1123456789,
+            'microseconds': 0},
         'offset': 0,
         'negative_utc': False,
     },
@@ -287,7 +293,9 @@
         'fullname': b'tony <ar@dumont.fr>',
     },
     'committer_date': {
-        'timestamp': 1127351742,
+        'timestamp': {
+            'seconds': 1127351742,
+            'microseconds': 0},
         'offset': 0,
         'negative_utc': False,
     },
@@ -389,7 +397,9 @@
         'fullname': b'olasd <nic@olasd.fr>',
     },
     'date': {
-        'timestamp': 1234567890,
+        'timestamp': {
+            'seconds': 1234567890,
+            'microseconds': 0},
         'offset': 42,
         'negative_utc': False,
     },
@@ -408,7 +418,9 @@
         'fullname': b'tony <ar@dumont.fr>',
     },
     'date': {
-        'timestamp': 1634366813,
+        'timestamp': {
+            'seconds': 1634366813,
+            'microseconds': 0},
         'offset': -120,
         'negative_utc': False,
     },
@@ -427,7 +439,9 @@
         'fullname': b'tony <tony@ardumont.fr>',
     },
     'date': {
-        'timestamp': 1634336813,
+        'timestamp': {
+            'seconds': 1634336813,
+            'microseconds': 0},
         'offset': 0,
         'negative_utc': False,
     },
diff --git a/swh/storage/tests/test_converters.py b/swh/storage/tests/test_converters.py
--- a/swh/storage/tests/test_converters.py
+++ b/swh/storage/tests/test_converters.py
@@ -12,6 +12,51 @@
     def setUp(self):
         self.maxDiff = None
 
+    def test_date_to_db(self):
+        date_to_db = converters.date_to_db
+        assert date_to_db(None) == {
+            "timestamp": None, "offset": 0, "neg_utc_offset": None}
+
+        assert date_to_db({
+            "timestamp": 1234567890,
+            "offset": 120,
+            "negative_utc": False,
+        }) == {
+            "timestamp": "2009-02-13T23:31:30+00:00",
+            "offset": 120,
+            "neg_utc_offset": False,
+        }
+
+        assert date_to_db({
+            "timestamp": 1123456789,
+            "offset": 0,
+            "negative_utc": True,
+        }) == {
+            "timestamp": "2005-08-07T23:19:49+00:00",
+            "offset": 0,
+            "neg_utc_offset": True,
+        }
+
+        assert date_to_db({
+            "timestamp": 1234567890,
+            "offset": 42,
+            "negative_utc": False,
+        }) == {
+            "timestamp": "2009-02-13T23:31:30+00:00",
+            "offset": 42,
+            "neg_utc_offset": False,
+        }
+
+        assert date_to_db({
+            "timestamp": 1634366813,
+            "offset": -120,
+            "negative_utc": False,
+        }) == {
+            "timestamp": "2021-10-16T06:46:53+00:00",
+            "offset": -120,
+            "neg_utc_offset": False,
+        }
+
     def test_db_to_author(self):
         # when
         actual_author = converters.db_to_author(